Cooperative behaviors in the evolution of antibiotic resistance

Abstract

Through a combination of experiments and modeling, I explored how inactivation of antibiotics by antibiotic-resistant bacteria affects the evolution of antibiotic resistance in two simple microbial communities. First, I examined the interaction between a resistant strain and a sensitive strain of the bacteria Escherichia coli in the presence of the [beta]-lactam antibiotic ampicillin. Second, I investigated whether two strains of Escherichia coli can form a cross-protection mutualism in a multi-drug environment containing the antibiotics ampicillin and chloramphenicol. In both experimental systems, I found that inactivation of antibiotics by resistant bacteria is an important cooperative behavior which enables microbes to help each other survive in otherwise lethal antibiotic concentrations. The rich dynamical behaviors that arise even in these simple systems highlight the inherent challenge in deciphering the workings of more complex microbial communities.